JAMA Dermatology has recently published the results of a retrospective cohort study evaluating the efficacy of supplementation with nicotinamide, vitamin B3, for the prevention of skin cancer. This study included data from nearly 34,000 patients in the Veterans Affairs Corporate Data Warehouse over a 25-year period, with analyses conducted both for the general population and a subset of recipients of solid organ transplants. Patients were considered exposed to nicotinamide if they had taken it at a dose of 500mg twice per day for at least 30 days, with the main outcome being time to the next skin cancer after baseline.
Overall, they report a significant 14% reduction in skin cancer risk with nicotinamide use, though if nicotinamide was initiated after the first skin cancer, the risk reduction was as high as 54%. The benefit declined when initiated after subsequent skin cancers, suggesting that supplementation after the initial skin cancer may have the largest preventative effect. A risk reduction was observed for skin cancers overall, basal cell carcinoma, and especially cutaneous squamous cell carcinoma.
While this was not a randomized trial, its large patient population does buttress a previously published phase 3 randomized and controlled trial, which found a 23% reduction in the risk for new non-melanoma skin cancers when supplemented at 500mg twice per day by people with a history of at least two non-melanoma skin cancers within the last 5 years. This study also reported a 13% lower incidence of actinic keratoses by the end of the 12-month study, with no difference in adverse events between groups over the course of the study.